Chapter 17 - Water Qualityeisdocs.dsdip.qld.gov.au/Lindeman Great Barrier... · Chapter 17 - Table...

1717Water Quality

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Chapter 17 - Table of Contents

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17 Water Quality 17-1

17.1 Introduction 17-1

17.2 Statutory Framework and Standards 17-2 17.2.1 Environmental Protection Act 1994 17-2 17.2.2 Environmental Protection (Water) Policy 2009 17-2

17.3 Water Quality Objectives 17-2 17.3.1 Site Description 17-2 17.3.2 Existing Water Quality 17-4 17.3.3 Water Quality Objectives 17-5 17.3.4 Water Quality Testing 17-9

17.4 Stormwater Quality Objectives 17-11 17.4.1 Construction Phase 17-11 17.4.2 Operational Phase 17-12

17.5 Stormwater Quality Management 17-13 17.5.1 Existing Stormwater Management 17-13 17.5.2 Proposed Stormwater Management 17-13

17.6 Stormwater Quality Modelling 17-18 17.6.1 Catchment Areas 17-19 17.6.2 Treatment Devices 17-22 17.6.3 MUSIC Results 17-23

17.7 Stormwater Quantity Modelling - Preliminary Detention Basin Sizing 17-26

17.8 Impacts associated with Climate Change 17-27

17.9 Potential Impacts and Mitigation Measures 17-28

17.10 Summary 17-31

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List of Figures Figure 17-1. Stormwater Catchments. ............................................................................................................ 17-3 Figure 17-2. Conceptual Diagram of Nutrient Pollutant Generation and Transport and Effects on the

Marine Environment. .................................................................................................................. 17-4 Figure 17-3. Stormwater Management Plan. .................................................................................................. 17-6 Figure 17-4. Bio-retention Garden in Central Median. .................................................................................. 17-14 Figure 17-5. Litter Basket. ............................................................................................................................ 17-15 Figure 17-6. MUSIC Land Use Areas. .......................................................................................................... 17-20 Figure 17-7. Conceptual Stormwater Treatment. ......................................................................................... 17-24

List of Tables Table 17-1. Existing water quality test results. ............................................................................................ 17-10 Table 17-2. MUSIC Rainfall Runoff Parameters. ........................................................................................ 17-18 Table 17-3. Mackay Pollutant Export Parameters. ...................................................................................... 17-18 Table 17-4. Proposed Developed Areas MUSIC Catchments. ................................................................... 17-21 Table 17-5. Entire Site Existing and Developed Case MUSIC Catchments. ............................................... 17-21 Table 17-6. MUSIC Results – Developed Areas. ........................................................................................ 17-23 Table 17-7. MUSIC Results – Comparison to Existing Case Pollutant Loads. ........................................... 17-25 Table 17-8. Average Annual Flows. ............................................................................................................ 17-25 Table 17-9. Rational Method Calculations. ................................................................................................. 17-26 Table 17-10. Preliminary Detention Basin Sizing. ......................................................................................... 17-27 Table 17-11. Risk assessment matrix – water quality. .................................................................................. 17-28

List of Maps

No table of figures entries found.

1 Introduction

2 Project Proponent

3 Site Description

4 Project Description

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17 Water Quality

17.1 Introduction

The proposed resort has been designed to protect and enhance the chemical and physical characteristics of

surface waters of the island and the Great Barrier Reef Marine Park. This chapter of the EIS provides an

assessment of water quality objectives applicable to the site and proposed stormwater management strategies

to mitigate potential impacts of any discharges from the proposed resort on sensitive receiving waters. It

details the chemical and physical characteristics of surface waters within the area that may be affected by the

project, including a description of water quality variability associated with climatic and seasonal factors.

The geotechnical assessment undertaken for the project found that the geology of the island is not one that is

conducive to the formation of aquifers and if groundwater does occur, it will be limited to areas of intense

fracturing of the rock (refer to Appendix F - Geotechnical Assessment). A review of historical data regarding

bore water extraction confirms this assessment and indicates that any groundwater resource is limited and

usually limited to short period of time following a rainfall event. Due to the unreliability and limited nature of

this resource, no extraction of groundwater resources is proposed.

The stormwater and water management strategy for the Lindeman Great Barrier Reef Resort Project aims to

reduce the pollutant load being discharged to streams that drain to the Great Barrier Reef Marine Park.

Specifically, stormwater and water management strategies will be adopted that:

Re-uses rainwater, reducing potable water demand and stormwater pollutant loads;

Treats and re-uses wastewater for non-potable uses on site;

Minimises the potential sources of stormwater pollutants;

Treats stormwater runoff to remove sediment and nutrient load;

Replicates existing flow patterns;

Reduces potential for scour and erosion; and

Integrates open space with stormwater drainage corridors and treatment areas to maximise public access and recreation and preserve waterway habitats and wildlife corridors.

This section provides a summary of the technical assessment undertaken by Cardno as provided in Appendix

P – Stormwater Management Plan and Water Balance Modelling. Further information regarding water and

sewage treatment infrastructure is included in Chapter 24 - Infrastructure.

Addendum: This EIS was initially prepared assuming that the safe harbour was to be part of the Lindeman

Great Barrier Reef Resort Project. With the commencement of the Great Barrier Reef Marine Park Authority’s

(GBRMPA) Dredging Coral Reef Habitat Policy (2016), further impacts on Great Barrier Reef coral reef habitats

from yet more bleaching, and the recent impacts from Tropical Cyclone Debbie, the proponent no longer seeks

assessment and approval to construct a safe harbour at Lindeman Island. Instead the proponent seeks

assessment and approval for upgrades to the existing jetty and additional moorings in sheltered locations

around the island to enable the resort’s marine craft to obtain safe shelter under a range of wind and wave

conditions. Accordingly, remaining references to, and images of, a safe harbour on various figures and maps

in the EIS are no longer current.

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17.2 Statutory Framework and Standards

17.2.1 Environmental Protection Act 1994

The Environmental Protection Act (EP Act) provides the legislative framework by which Queensland's

environment is protected while allowing for development that improves the total quality of life, both now and in

the future. Specifically, the EP Act seeks to maintain a range of environmental values including:

(a) a quality or physical characteristic of the environment that is conducive to ecological health or public

amenity or safety; or

(b) another quality of the environment identified and declared to be an environmental value under an

environmental protection policy or regulation.

For the purposes of the environmental impact statement, reference is made to the environmental values

provided in the Environmental Protection (Water) Policy 2009 (EPP Water) established under the EP Act. The

following sections provide an overview of the environmental values identified in this policy along with the

objectives established achieve their protection.

17.2.2 Environmental Protection (Water) Policy 2009

The EPP (Water) provides that the environmental values (section 6(2)(a)) to be enhanced or protected under

this policy are:

(a) for high ecological value waters—the biological integrity of an aquatic ecosystem that is effectively

unmodified or highly valued;

(b) for slightly disturbed waters—the biological integrity of an aquatic ecosystem that has effectively

unmodified biological indicators, but slightly modified physical, chemical or other indicators;

(c) for moderately disturbed waters—the biological integrity of an aquatic ecosystem that is adversely

affected by human activity to a relatively small but measurable degree;

…

(h) for waters that may be used for recreation or aesthetic purposes, the suitability of the water for—

(i) primary recreational use; or

(ii) secondary recreational use; or

(iii) visual recreational use;

(i) for waters that may be used for drinking water—the suitability of the water for supply as drinking

water.

17.3 Water Quality Objectives

17.3.1 Site Description

The site has an existing resort, golf course, maintenance facilities and a dam, which supplies all water

requirements for the resort. Gap Creek and several other small ephemeral freshwater streams traverse the

site and discharge to the ocean, as shown in Figure 17-1. Due to the steepness of the island these freshwater

streams have negligible interaction with tidal waters, as the tidal zone on the island is limited in area. The

extent of development is mostly contained to cleared or previously developed areas. Eco villas are proposed

to be constructed in previous golf course and densely vegetated areas around the perimeter of the site.

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Figure 17-1. Stormwater Catchments.

Flow Path

Diverted Catchment

Stormwater Management

1m Contour

X Note: A safe harbour is no longer proposed.

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17.3.2 Existing Water Quality

The water quality of the Mackay Whitsundays is under pressure from land uses such as agriculture, forestry,

grazing and urban. Increased nutrients, sediment and herbicide loads resulting from development have

impacted negatively on the health of the Great Barrier Reef (GBR). Urban and other intensive uses (including

sewage treatment plants) account for just over 10% of the total regional particulate nutrient load, and 4% of

the regional dissolved organic load (Mackay Whitsundays Water Quality Improvement Plan 2014-2021

(WQIP)). The schematic from the Mackay Whitsundays WQIP demonstrating the different pressures and

impacts is shown in Figure 17-2.

Figure 17-2. Conceptual Diagram of Nutrient Pollutant Generation and Transport and Effects on the Marine Environment.

The Healthy Rivers to Reef Partnership 2014 Pilot Report Card gave the Inshore Marine Whitsunday

waterways a rating of C/ Moderate. This was based on a moderate score for water quality and coral and a poor

score for seagrass. The moderate condition of the existing water quality highlights the need for the

development to ensure that the potential for additional nutrients, sediments, pesticides and herbicides to be

discharged from the site is limited. Water quality is naturally variable, and is dependent on numerous factors

such as land use, catchment management practices, antecedent conditions, soil types, climatic and seasonal

factors and in-stream processes. Tropical rivers and creeks are characterised by minimal flows in the winter

dry season, which generally have low dissolved oxygen, low nitrogen and phosphorous levels, and low turbidity

levels. During the summer wet seasons, “first flush” run-off can be acidic with elevated levels of suspended

solids, nutrients, sulphates and heavy metals. During extreme events there is potential for high levels of

pollutants to be discharged to the marine receiving environment if catchment areas are not appropriately

managed.

Two rounds of event based testing were able to be conducted at the site within the waterways for sites LIND01

– LIND06 (refer to Figure 17-3). The results are provided in section 17.3.4 and Appendix P - Stormwater

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Management Plan and Water Balance Modelling. Based on the event based WQOs the current water

quality meets objectives, with one elevated recording for suspended solids.

17.3.3 Water Quality Objectives

The water quality objectives were sourced from the Environmental Protection (Water) Policy 2009 (EPP

(Water) 2009) Proserpine River, Whitsunday Island and O'Connell River Basins Environmental Values and

Water Quality Objectives and associated plans. The Water Quality Guidelines for the Great Barrier Reef Marine

Park 2010 were also referenced.

17.3.3.1 Freshwater

Based on Table 1 of EPP (Water) 2009, the relevant environmental values for Lindeman Island’s fresh waters

(i.e. Whitsunday Islands fresh waters) include:

Aquatic Ecosystems;

Irrigation;

Secondary Recreation;

Visual Recreation;

Drinking Water; and

Cultural and Spiritual Values.

The majority of Lindeman Island is classified as Whitsunday Island freshwater with High Ecological Value

(HEV) for Aquatic Ecosystems (HEV2384) (refer to Figure 17-3). However, the existing and proposed

developed area of Lindeman Island (with the exception of glamping area on the western coast) is not included

in this area and is therefore classified as Moderately Disturbed Freshwater.

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Figure 17-3. Stormwater Management Plan.

HEV: High Ecological Value

MD: Moderately Disturbed

SD: Slightly Disturbed

Water Quality Monitoring Site

EPP Water

LIND07

LIND02

LIND01

LIND03

LIND06

LIND04 LIND05

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The water quality objectives for this area are:

Aquatic Ecosystem – moderately disturbed (MD)

Ambient (baseflow). In the absence of more locally applicable information, WQOs for Whitsunday

Islands fresh waters at the moderately disturbed level of protection are based on the 20th/80th

percentile of WQOs for Repulse Creek subcatchment (mainland):

Dissolved inorganic nitrogen: <31 μg/L

Particulate N: <52 μg/L

Filterable reactive phosphorus (FRP): <15 μg/L

Particulate phosphorus: <17 μg/L

Dissolved oxygen:

i. No-flow 20th and 80th percentile: 50 to 120% saturation

ii. Flow 20th and 80th percentile: 90 to 105% saturation

Suspended solids: <3 mg/L

pH: 7.2-7.6

Electrical conductivity (EC): <780 μS/cm

Ametryn: <LOD

Atrazine: <LOD

Diuron: <LOD

Hexazinone: <LOD

Tebuthiuron: <LOD

As the freshwater streams on Lindeman Island are ephemeral limited opportunity exists to undertake baseflow

monitoring. No specific water quality objectives are provided for events in EPP (Water) 2009. However, Table

31 of the Mackay Whitsundays WQIP has the following event-based WQOs for moderately disturbed

freshwater streams in Repulse Creek (which is used to define WQOs for Whitsunday Islands):

Dissolved inorganic nitrogen: <256 µg/L

Particulate N: <261 µg/L

Filterable reactive phosphorus (FRP): <27 µg/L

Particulate phosphorus: <31 µg/L

Suspended solids: <8 mg/L

Secondary Contact Recreation

Objectives as per NHMRC (2008), including:

intestinal enterococci: 95th percentile ≤ 40 organisms per 100mL (for healthy adults) (NHMRC, 2008; Table 5.7)

cyanobacteria/algae—refer objectives for primary recreation, NHMRC (2008), i.e.:

Level 1: ≥ 10 μg/L total microcystins; or ≥ 50 000 cells/mL toxic Microcystis aeruginosa; or biovolume equivalent of ≥ 4 mm3/L for the combined total of all

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cyanobacteria where a known toxin producer is dominant in the total biovolume or

Level 2: ≥ 10 mm3/L for total biovolume of all cyanobacterial material where known toxins are not present

cyanobacterial scums consistently present.

Visual Recreation

Recreational water bodies should be aesthetically acceptable to recreational users. The water should be free from visible materials that may settle to form objectionable deposits; floating debris, oil, scum and other matter; substances producing objectionable colour, odour, taste or turbidity; and substances and conditions that produce undesirable aquatic life.

Drinking Water

The drinking water quality objectives for the dam, before treatment are:

Giardia: 0 cysts (Queensland Water Supply Regulator). If Giardia is detected in drinking water then the health authorities should be notified immediately and an investigation of the likely sources of contamination undertaken.

Cryptosporidium: 0 cysts (Queensland Water Supply Regulator). If Cryptosporidium is detected in drinking water then the health authorities should be notified immediately and an investigation of the likely sources of contamination undertaken.

E. coli: <100 cfu/100mL

Enterococci: <100 cfu/100mL

Blue green algae (cyanobacteria): <10000 cells/mL

Algal toxin: <1 µg/L Microcystin

Turbidity: <30 NTU

Colour: <35 TCU

pH: 6.5-8.0

Total hardness: <115mg/L

Conductivity: <300 µS/cm

Total dissolved solids: ADWG 2011 aesthetic guideline: <600 mg/L

Total organic carbon: <2 mg/L

Sodium: <25 mg/L

Sulfate: <4 mg/L

Dissolved oxygen: >80% saturation

Pesticides: <0.1 µg/L for individual compound, <1.0 µg/L combined total for all compounds

Visual Recreation

> Recreational water bodies should be aesthetically acceptable to recreational users. The water should be free from visible materials that may settle to form objectionable deposits; floating debris, oil, scum and other matter; substances producing objectionable colour, odour, taste or turbidity; and substances and conditions that produce undesirable aquatic life.

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Cultural and Spiritual Values

> Protect or restore indigenous and non-indigenous cultural heritage consistent with relevant policies and plans.

17.3.3.2 Coastal and Marine Waters

The Water Quality Guidelines for the Great Barrier Reef Marine Park (2010) describe the concentrations and

trigger values for sediment, nutrients and pesticides that have been established as necessary for the protection

and maintenance of marine species and ecosystem health of the Great Barrier Reef. Parameters that are not

listed default to the Queensland Water Quality Guidelines, which in turn default to the Australian and New

Zealand Guidelines for Fresh and Marine Water Quality. Gap Creek and several other small ephemeral

freshwater streams traverse the site and discharge to the ocean, as shown in Figure 17-1. Due to the

steepness of the island these freshwater streams have negligible interaction with tidal waters, because the

tidal zone on the island is limited to the shoreline area.

The stormwater and water management strategy for the Lindeman Great Barrier Reef Resort Project aims to

reduce the pollutant load being discharged to streams that drain to the Great Barrier Reef Marine Park.

Specifically, stormwater and water management strategies will be adopted that:

Re-use rainwater, reducing potable and irrigation water demand and stormwater pollutant loads;

Treat and re-use wastewater for non-potable uses on site;

Minimise the potential sources of stormwater pollutants;

Treat storm water runoff to remove sediment and nutrient load;

Replicate existing flow patterns;

Reduce potential for scour and erosion; and

Integrate open space with stormwater drainage corridors and treatment areas to maximise public access and recreation and preserve waterway habitats and wildlife corridors

17.3.4 Water Quality Testing

17.3.4.1 Existing Conditions and Monitoring


monitoring. Despite this, two rounds of event based testing were able to be conducted at the site within the

waterways. For the March 2016 event, there were two rounds of sampling were conducted for sites LIND 1 -

6 for the same event due to issues with transporting samples from the island. Given the recommended holding

times, only the later results have been referenced. For the June 2016 event it was not possible to undertake

sampling at LIND05. The results are provided in Appendix P – Stormwater Management Plan and Water

Balance Modelling, with the median and range of results summarised below in Table 17-1.

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Table 17-1. Existing water quality test results.

Parameter Median Concentration (mg/L)

Mar-16 Jun-16 Event Based WQO

Suspended Solids <5 5 8

Total Nitrogen 0.35 0.70 n/a

Dissolved Inorganic Nitrogen 0.035 0.049 0.256

Total Phosphorus 0.03 0.04 n/a

Filterable Reactive Phosphorus 0.01 0.006 0.027

Parameter Range of Results

Mar-16 Jun-16 Event Based WQO

Suspended Solids <5 <5 to 14 8

Total Nitrogen 0.2 to 0.6 0.55 to 0.98 n/a

Dissolved Inorganic Nitrogen 0.02 to 0.06 0.034 to 0.09 0.256

Total Phosphorus 0.02 to 0.05 0.02 to 0.06 n/a

Filterable Reactive Phosphorus <0.01 to 0.02 <0.005 to 0.019 0.027

In terms of the monitoring points LIND01 is located within the existing dam and LIND02 – LIND06 is normally dry and as such sampling can only take place immediately after a rainfall event. LIND07 is a new proposed monitoring point located over at the proposed glamping facility.

Based on the event based WQOs listed in section 17.3.3, the current water quality meets the specified objectives. In June, at site LIND06 there was an elevated level of TSS.

Further additional water quality testing is proposed at the terrestrial sites prior to the commencement of construction in accordance with the following proposed sampling schedule. Additionally, the proponent has made a commitment to completing a baseline marine water quality sampling program. The objective of the program would be to identify the environmental values of receiving waters and set objectives and indicators relevant to the protection of those values.

Table 17-2. Sampling Schedule.

TEST PARAMETER HOLDING TIMES

Total Suspended Solids 7 days

Nitrogen Compounds TN, TKN and NH3 – 28 days

Nitrate and Nitrites – 2 days

Phosphorous Compounds Reactive – 2 days

Total – 28 days

Chlorophyll A 2 days

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17.3.4.2 Construction

Undertake water quality testing as close as possible to each month (noting that as the streams are ephemeral

this will be determined by rainfall events) during construction at locations indicated in Figure 17-3. The WQOs

will be determined based on the results of the water quality monitoring, with the purpose of carrying out the 12

months of monitoring is to set these WQOs.

17.3.4.3 Operation

If the proposed stormwater treatment devices are modelled using MUSIC, detailed based on Healthy

Waterways guidelines and constructed as detailed, then regular water quality monitoring during operation is

not required. However, to confirm compliance, event based freshwater quality testing is to be conducted at

least once a year at locations shown in Figure 17-3. Regular water quality monitoring of the dam and at the

WTP will be required for drinking water purposes. Regular water quality monitoring at the STP will be required

to ensure suitability for irrigation and re-use.

17.4 Stormwater Quality Objectives

17.4.1 Construction Phase

During the construction phase, the potential exists for significant increases in the amount of pollutants,

particularly sediment, to be exported from the site. An Erosion and Sediment Control Program (ESCP) will be

required to be prepared for the site prior to construction in accordance with the Environmental Management

Plan (EMP) refer to chapter 28 of the EIS. The ESCP must:

Be consistent with current best management practice guidelines such as the IECA Best Practice Erosion and Sediment Control;

Prescribe non-structural controls where applicable, such as minimising the extent and duration of soil exposure, diversion of upstream catchments around disturbed areas, staging the works, identifying areas for protection and delaying clearing until construction works are imminent;

Include a maintenance schedule for ensuring ESC and stormwater infrastructure is maintained in effective working order;

Include an adaptive management program to identify and rectify non compliances and deficiencies in environmental performance;

Include contingency management measure for the site, for example to ensure ESC measures are effective at all times, particularly just prior to, during and after wet weather;

For each phase of works detail the types, location, sequence and timing of measures and actions to effectively minimise erosion, manage flows and capture sediment;

Be consistent with current best management practice standards, taking into account all environmental constraints including erosion hazard, season, climate, soil and proximity to waterways;

Be prepared to a sufficient standard and level of detail with supporting documentation;

Include an effective monitoring and assessment program to identify, measure, record and report on the effectiveness of ESCs and the lawfulness of releases; and

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Be prepared by a suitably qualified and experienced professional.

The release limits for stormwater captured in a sediment basin are not to exceed the following limits:

Total Suspended Solids (TSS): 50 mg/L;

Turbidity (NTU): less than 10% above background; and

pH: 6.5 – 8.5.

No development, besides glamping on the western beach, is proposed within HEV areas.

17.4.2 Operational Phase

Stormwater Quality

The water quality objectives for the stormwater quality treatment measures proposed throughout the

development were sourced from State Planning Policy, July 2014, for the Central Queensland (north) climatic

region. They specify a minimum reduction in mean annual pollutant loads, when compared to an unmitigated

catchment. The water quality objectives for the post construction phase are:

75% reduction in Total Suspended Solids (TSS);

60% reduction in Total Phosphorus (TP);

35% reduction in Total Nitrogen (TN); and

90% reduction in Gross Pollutants (>5mm).

It should be noted that Mackay Regional Council has adopted a lower target of 35% removal of TN than

required by other Councils in this climatic region. A sensitivity analysis was conducted to determine the impact

on sizing of treatment devices if a higher TN removal objective was targeted.

Waterway stability management

This objective is applicable if runoff from a site drains to or passes through natural channels, non-tidal

waterways or wetlands. As parts of the development is draining to a non-tidal waterway it is required to provide

attenuation of peak discharges to match the existing case for the 63% Annual Exceedance Probability (AEP)

event. It is considered that this objective will be satisfied by the Water Sensitive Urban Design (WSUD)

measures proposed throughout the development, which will provide some attenuation of peak flows in minor

storm events. The upstream dam diversion will also reduce flows during minor events. Outlets from WSUD

devices will be designed to evenly disperse flow or will be provided with appropriate scour protection, so as to

reduce the potential for scour of downstream waterways.

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17.5 Stormwater Quality Management

17.5.1 Existing Stormwater Management

Vegetated swales located around the site currently provide some polishing of stormwater before it is

discharged off site. No other stormwater treatment measures, such as Gross Pollutant Traps (GPTs) are

currently provided.

17.5.2 Proposed Stormwater Management

17.5.2.1 Suitable Stormwater Treatment Devices

Rainwater Harvesting

The development is required to provide its own water supply via the existing dam. In order to increase the

reliability of this supply a number of measures are proposed to be implemented. One of these measures is to

use rainwater harvesting for pool top up and toilet flushing for villas, and provide a priority source of water at

the WTP. Rainwater harvesting has the added benefit of reducing the stormwater and associated pollutant

load being discharged downstream, and improving waterway stability. The estimated reduction in potable

water demand from rainwater harvesting is 21.2 ML/year. The following minimum tank volumes and

contributing catchment areas will be provided:

10kL for each villa, draining a minimum roof area of 100m2, with a pool surface area of 25m2.

500kL for resort pools, draining a minimum roof area of 3500m2, with a pool surface area of 3000m2.

350kL for additional rainwater harvesting near Water Treatment Plant (WTP), draining a minimum roof area of 6300m2.

In order to further improve the reliability of the water supply as much roof area as practical should be directed

to rainwater tanks.

Revegetation/Buffer Areas

A large proportion of the existing development footprint is cleared for use as a golf course. The majority of the

proposed new development area will be located within these cleared areas and the golf course will be reduced

in size. Revegetation around the proposed site with native vegetation will reduce the runoff and associated

pollutant load. Vegetated buffer areas between waterways and development areas will be provided. The

paths around the development will be allowed to sheet flow to these buffer areas, avoiding the concentration

of runoff.

Vegetated Swales

The continued use of vegetated swales throughout the site will reduce pollutant loads by slowing flow velocities

and filtering pollutants.

Bio-retention Gardens and Basins

Bio-retention gardens treat stormwater runoff “at-source”, before it is discharged to the stormwater pipes. They

treat stormwater by allowing it to slowly percolate through the vegetated filtration media, where filtration,

adsorption and some biological uptake occurs. They are particularly suited to the removal of nutrients. They

are effective treatment devices in areas where the location of an end-of-line basin is impractical as they do not

need as much vertical differentiation and can be integrated into the landscape design. Bio-retention gardens

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can be accommodated “on-line”, i.e. with field inlets located within the garden area, or “off-line”, i.e. excess

stormwater overflows to standard gully inlets located downstream of gardens. If located “on-line” then

additional depth above the field inlet is required so that ponding external to the garden area is minimised.

Appropriate batters or edge treatments are required for safety purposes. Alternatively, raised bio-retention

gardens can be provided to treat excess runoff from roof water not directed to rainwater tanks. If the filter

media depth is increased to a minimum of 0.8 metres then they can also be planted with trees. The extended

detention depth (EDD) provided in bio-retention gardens is generally less than provided for bio-retention basins

so as to allow for their integration into landscape areas at street level. An EDD of 0.1m was assumed in the

MUSIC modelling. Bio-retention basins are similar to bio-retention gardens except that they are located end-

of-line, are larger in area and have increased EDD (0.3m assumed in MUSIC modelling). Coarse sediment

forebays are required on the inlets, and measures to avoid damage to vegetation and filter media during high

flows should be accommodated in the design. Bio-retention basins require less overall area than bio-retention

gardens due to their increased EDD and their reduced batter extents. Bio-retention gardens and basins should

be planted with vegetation that is proven to be effective at reducing nutrients and tolerating periods of

inundation. During prolonged dry periods it may be necessary to irrigate with treated wastewater.

Figure 17-4. Bio-retention Garden in Central Median.

Constructed Wetlands

Constructed wetlands are shallow, densely vegetated waterbodies that use sedimentation, filtration and

biological uptake processes to treat stormwater. Outlets are sized so that water is released slowly over a few

days. They require a variety of water depths and vegetation zones. They provide habitat and potential storage

of water for re-use. They typically require areas significantly larger than needed for bio-retention systems, but

can be installed end-of-line in vertically constrained areas. A GPT or sedimentation basin is often used to

provide pre-treatment of flows entering the wetland and high flow bypasses are required so that damage to

the wetland is avoided in major storm events. Due to the presence of rock at shallow depths the use of

constructed wetlands for treatment of stormwater runoff may be more practical in relatively flat areas of the

site, if excavation can be minimised.

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Litter Baskets

Litter baskets are installed within field and gully inlets, capturing gross pollutants and sediment before they are

discharged to the stormwater network. Although not included in the MUSIC treatment train they should be

considered in areas where high litter levels are likely. They can be cleaned manually or by vacuum truck.

Figure 17-5. Litter Basket.

Proprietary Treatment Devices

There are numerous proprietary stormwater treatment devices available that can provide primary, secondary

or tertiary treatment of stormwater using either mechanical or biological methods. Some are able to treat

stormwater to a high enough level to meet all stormwater pollutant removal targets. They require less area

than standard stormwater treatment devices and can be located at end-of-line without the need for significant

vertical differentiation. However, the cost and practicality of ongoing maintenance should be considered. They

might be appropriate for use in areas when standard bio-retention gardens or basins cannot be

accommodated, or areas with specific pollutant loads, such as re-fuelling areas. Proprietary devices have not

been included in the MUSIC treatment train.

Porous Pavement

Due to the presence of rock at shallow depths and the steepness of the majority of the site the use of porous

pavement is not considered to be practical at this site. However, it should be considered for use in low traffic,

relatively flat areas where adequate underdrainage can be accommodated.

17.5.2.2 Proposed Stormwater Treatment Devices

MUSIC modelling has been conducted to determine the stormwater quality treatment devices required to meet

pollutant load objectives. The proposed stormwater treatment devices include:

> Rainwater Harvesting:

- 10kL for each villa, draining a minimum roof area of 100m2, with a pool surface area of 25m2.

- 500kL for resort pools, draining a minimum roof area of 3500m2, with a pool surface area of 3000m2.

- 350kL for additional rainwater harvesting near Water Treatment Plant (WTP), draining a minimum roof area of 6300m2.

> Vegetated Buffers for Paths to Villas;

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> Vegetated Swales maintained throughout site;

> Treatment of runoff from remaining impervious areas (not directed to rainwater tanks) from Resort units, communal facilities and maintenance and service areas to following requirements:

- Bio-retention Gardens within landscape areas with a minimum filter surface area equivalent to 0.9% of the contributing catchment area. Minimum filter depth of 0.4m and EDD of 0.1m assumed;

- Raised Bio-retention Gardens treating roof runoff not directed to tanks with a minimum filter surface area equivalent to 0.6% of the contributing catchment area. Minimum filter depth of 0.4m and EDD of 0.3m assumed;

- End-of-line Bio-retention Basins with a minimum filter surface area equivalent to 0.6% of the contributing catchment area. Minimum filter depth of 0.4m and EDD of 0.3m assumed; OR

- Constructed Wetlands with a surface area equivalent to 5% of the contributing catchment area. Minimum detention time of 48 hours and EDD of 0.5m assumed. Constructed wetlands will be provided with GPTs or sedimentation basins for pre-treatment.

> Litter baskets or GPTs for areas with high levels of litter expected.

> Proprietary Treatment devices where the use of standard Water Sensitive Urban Design (WSUD) is not suitable.

Point and Diffuse Sources

Diffuse sources of pollution potentially include run-off from urban areas such as roads, runway, footpaths and

other sealed surfaces, while the point sources include the areas in the services infrastructure precinct such as

the diesel storage tanks. The runoff from the runway and surrounding hardstand areas will be directed via

grassed swales to stormwater treatment areas. Underground spill containment storage be provided upstream

of these treatment areas. The MUSIC modelling assumed that villa roof area not directed to rainwater tanks

would be treated by buffer areas and grassed swales. However, it is recommended that raised bio-retention

gardens be provided for roofwater runoff not connected to tanks, particularly for villas located near waterways.

This option was not included in the MUSIC modelling. The outlets of all rainwater tanks and stormwater

treatment devices will be designed to disperse flow to avoid scour and erosion.

Point sources will be managed through the enclosure and bunding of areas to be used for the storage of

hazardous materials, including roofing of such areas to minimise the potential for overflow. Any stormwater

captured within bunded areas used for the storage and/handling of wastes or other hazardous materials shall

be pumped-out and disposed of at an appropriately licensed facility on the mainland. Refer to Chapter 23 –

Contamination and Chapter 24 – Infrastructure.

17.5.2.3 Stormwater Quality Management Strategies

The prevention of pollution is the most effective means of reducing pollutant loads. The following management

strategies will be adopted on site:

(a) Use of pesticides, herbicides or fertilisers throughout the development is to be avoided. Appropriate landscaping will be used to minimise their requirements. If necessary they are not to be applied during the wet season months of January to March and a buffer of at least 20 metres to all waterways is to be maintained. Organic pesticide alternatives should be used if possible;

(b) Application of irrigation water will occur in areas with appropriate buffers;

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(c) All potentially hazardous materials and waste (e.g. waste oils, batteries, fuels and chemical wastes etc.) shall be stored in separate containers located within a bunded and roofed hardstand area;

(d) Refuelling areas will be bunded with a stormwater containment system to prevent discharge to soil or waterways.

(e) A spill response procedure shall be established and implemented, and appropriate clean up equipment and materials shall be provided where any construction activities or waste storage activities are undertaken to prevent the contamination of stormwater;

(f) Any stormwater captured within bunded areas used for the storage, refuelling or handling of fuels, waste or other hazardous materials shall be pumped out and disposed of at an appropriately licensed facility on the mainland;

(g) Regular inspections and maintenance will be undertaken for stormwater drainage and treatment systems;

(h) Runoff from golf course areas will be managed in accordance with the Golf Course Management Plan and the Irrigation Management Plan (refer to Chapter 28 – Environmental Management Plan) with any runoff directed towards vegetated buffer areas. In accordance with point (a) use of pesticides, herbicides or fertilisers will be avoided where possible but if required they are not to be applied during the wet season months of January to March and a buffer of at least 20 metres to all waterways is to be maintained. Organic pesticide alternatives should be used if possible. Any nutrients will be taken up by the vegetation;

(i) Monitoring of soil nutrient levels to prevent leaching of nitrogen and phosphates;

(j) Monitoring of water quality throughout the development to identify potential non-compliances;

(k) Bins will be provided around the development for the collection of litter and these will be regularly emptied;

(l) Landscape maintenance measures will include collection of all garden litter for composting in controlled areas. No disposal to waterways is to be allowed;

(m) Staff training will include awareness of environmental issues; and

(n) Issues relating to stormwater quality will be recorded in the Environmental Incident Register, and appropriate actions will be taken.

The catchment which discharges to the existing dam on the island is generally undisturbed, with some existing

golf course area. Consequently, the quality of the water in the dam is very good. A restaurant and several

villas are proposed within the dam catchment. These will be provided with a high level of stormwater quality

treatment. Regular monitoring of the dam water quality will be carried out as part of the project to ensure

appropriate quality is maintained. Best practice water quality treatment measures will be implemented and

maintained at all times through the construction and operational phases. A detailed Environmental

Management Plan (EMP) will be prepared prior to any construction work commencing, detailing the proposed

techniques to be employed around the study area.

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17.6 Stormwater Quality Modelling

The proposed development was modelled in MUSIC Version 6.1.0 based on 10 years of 6 minute rainfall data

at Mackay M.O Station 33119 (1/1/1990 to 31/12/1999) was used for the analysis. The MUSIC source nodes

were based on the values for urban, rural residential, forest and commercial land uses, as outlined in the

Mackay Regional Council MUSIC Guidelines – Version 1.1 2008 (Mackay Regional Council, 2008). The

adopted source nodes are summarised in Table 17-3 and Table 17-4. The upland soil typology node was used

to define the rainfall-runoff characteristics, as this was considered to be characteristic of the soils encountered

at the site. The urban source nodes were used for the majority of the developed areas as these are

recommended for use in residential developments with small areas of commercial use.

Table 17-3. MUSIC Rainfall Runoff Parameters.

Parameter Value

Soil Typology Upland

Rainfall threshold (mm) 1

Soil storage capacity (mm) 200

Initial storage (% capacity) 30

Field capacity (mm) 80

Infiltration capacity coefficient a 200

Infiltration capacity exponent b 1

Initial depth (mm) 10

Daily recharge rate (%) 0.5

Daily baseflow rate (%) 0.16

Daily deep seepage rate (%) 2

Table 17-4. Mackay Pollutant Export Parameters.

Parameter Surface Type

TSS Log10 Values TP Log10 Values TN Log10 Values

Mean Std. Dev Mean Std. Dev Mean Std. Dev

Urban

Baseflow

Roof N/A N/A N/A N/A N/A N/A

Roads 1.00 0.34 -0.97 0.31 0.20 0.20

Ground 1.00 0.34 -0.97 0.31 0.20 0.20

Combined 1.00 0.34 -0.97 0.31 0.20 0.20

Stormflow

Roof 1.30 0.39 -0.89 0.31 0.26 0.23

Roads 2.43 0.39 -0.30 0.31 0.26 0.23

Ground 2.18 0.39 -0.47 0.31 0.26 0.23

Combined 2.18 0.39 -0.47 0.32 0.26 0.23

Commercial

Baseflow

Roof N/A N/A N/A N/A N/A N/A

Roads 0.78 0.39 -0.60 0.50 0.32 0.30

Ground 0.78 0.39 -0.60 0.50 0.32 0.30

Combined 0.78 0.39 -0.60 0.50 0.32 0.30

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Parameter Surface Type

TSS Log10 Values TP Log10 Values TN Log10 Values

Mean Std. Dev Mean Std. Dev Mean Std. Dev

Stormflow

Roof 1.30 0.38 -0.89 0.34 0.25 0.34

Roads 2.43 0.38 -0.30 0.34 0.37 0.34

Ground 2.16 0.38 -0.39 0.34 0.37 0.34

Combined 2.16 0.38 -0.39 0.34 0.37 0.34

Rural Residential

Baseflow Combined 0.53 0.24 -1.54 0.38 -0.52 0.39

Stormflow Combined 2.26 0.51 -0.56 0.28 0.32 0.30

Forest

Baseflow Combined 0.51 0.28 -1.79 0.28 -0.59 0.22

Stormflow Combined 1.90 0.20 -1.10 0.22 -0.075 0.24

17.6.1 Catchment Areas

The site was broken down into different land use areas as shown in Figure 17-6. The catchment parameters

used in the MUSIC analysis are summarised in Table 17-5 and Table 17-6. Two MUSIC models were set up:

one that included only developed mainly impervious areas of the site for compliance with stormwater quality

objectives (refer Table 17-5) and another that included the full extent of development, including bushland and

golf course areas (refer Table 17-6). The second model was set up to allow comparison to the existing

pollutant loads.

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Figure 17-6. MUSIC Land Use Areas.

MUSIC Land Use Area (Villas and Paths also included in MUSIC Analysis)

Extent of Total Site Extent of MUSIC Analysis


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Table 17-5. Proposed Developed Areas MUSIC Catchments.

Catchment Name Source Type Area

(ha) Fraction Impervious

Resort Roof to Tank Urban Roof 0.350 1.0

Maintenance Roof to Tank Urban Roof 0.630 1.0

Villa Roof to Tank Urban Roof 0.945 1.0

Villa Roof Urban Roof 0.945 1.0

Villa Paths Urban Road 2.500 0.8

Resort Urban Combined 5.910 0.6

Resort d/s of Swale Urban Combined 2.810 0.6

Maintenance Facilities Urban Combined 2.820 0.8

Runway Pavement Commercial Road 4.665 1.0

Table 17-6. Entire Site Existing and Developed Case MUSIC Catchments.

Catchment Name Source Type Area

(ha) Fraction Impervious

Entire Developed Site

Resort Roof to Tank Urban Roof 0.350 1.0

Maintenance Roof to Tank Urban Roof 0.630 1.0

Villa Roof to Tank Urban Roof 0.945 1.0

Villa Roof Urban Roof 0.945 1.0

Villa Paths Urban Road 2.500 0.8



Maintenance Facilities Urban Combined 2.820 0.8


Runway Grass Rural Residential 4.665 0.0

Golf Course Grassed Area Rural Residential 7.440 0.0

Forest Forest 42.740 0.0

Entire Existing Site



Maintenance Urban Combined 3.450 0.7


Runway Grass Rural Residential 7.903 0.0

Golf Course Rural Residential 14.960 0.0

Caretaker Rural Residential 1.840 0.15

Forest Forest 38.920 0.0

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17.6.2 Treatment Devices

Rainwater Tanks

The rainwater tank demands were taken from the results of the GoldSim modelling. The villa rainwater tanks

are to be used for toilet flushing and pool top up; the resort tanks are to be used for pool top and the

maintenance area tanks are be used as a source of water at the WTP. The rainwater demands were:

> 14.0 ML/year, scaled on PET-rain for 189 10kL (total storage of 1890kL) villa rainwater tanks.

> 6.3 ML/year, scaled on PET-rain for a 500kL resort rainwater tank. This rainwater tank is to be divided proportionally between communal resort pools.

> 21.2 kL/day (7.7ML/year) for additional rainwater harvesting from 350kL maintenance area tank.

Buffer Areas

Buffer areas were used to treat runoff from villa rooves and paths, as revegetation of cleared areas is proposed.

It was assumed that they treated 100% of the upstream catchment and were equivalent to 50% of the upstream

impervious area.

Vegetated Swale

A 10 metre wide swale with 1 metre wide base, depth of 0.5m and a bed slope of 3 percent was used to

represent the numerous grassed swales located throughout the development.

Option 1 - Bio-retention Gardens

Bio-retention gardens were modelled as being 0.9% of the contributing catchment with an EDD of 0.1m and a

minimum filter depth of 0.4m. The filter media and surface area were assumed to be equal. The filter media

was assumed to be sandy loam, with a saturated hydraulic conductivity of 200mm/hr, a TN content of 300

mg/kg and an orthophosphate content of 20 mg/L. The gardens were assumed to be vegetated with effective

nutrient removal plants and the overflow weir width was assumed to be one tenth of the filter media area.

Option 2 - Bio-retention Basins

Bio-retention basins were modelled as being 0.6% of the contributing catchment with an EDD of 0.3m and a

filter depth of 0.4m. The filter media and surface area were assumed to be equal. The filter media was

assumed to be sandy loam, with a saturated hydraulic conductivity of 200mm/hr, a TN content of 300 mg/kg

and an orthophosphate content of 20 mg/L. The basins were assumed to be vegetated with effective nutrient

removal plants and the overflow weir width was assumed to be one tenth of the filter media area.

Option 3 - Constructed Wetland

Constructed wetlands were modelled as being 5% of the contributing catchment with an EDD of 0.5m, a

permanent pool volume equivalent to an average depth of 0.3m and an outlet sized to provide 48 hours of

detention time. GPTs or sedimentation basins should be provided on the inlets.

Litter Baskets and GPTs

No litter baskets, GPTs or proprietary devices were included in the MUSIC modelling. However these should

be considered for use in some areas.

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17.6.3 MUSIC Results

Pollutant Load Removal

The results of MUSIC for the pollutant load analysis for the developed areas of the site are summarised in

Table 17-7. MUSIC Results – Developed Areas. As demonstrated by this table, all treatment options meet

the required pollutant load reduction targets. The limiting pollutant is TN for all treatment options.

Table 17-7. MUSIC Results – Developed Areas.

Pollutant

Pollutant Load

(kg/year)

% Pollutant Load Removed

IN Option 1

OUT

Option

1

Option

2

Option

3

Water Quality

Objective

Flow (ML/year) 287 265 7.8 7.3 13.1 n/a

Total Suspended Solids 71,300 11,200 84.3 83.6 90.1 75

Total Phosphorus 134 45.3 66.1 65.5 70.1 60

Total Nitrogen 711 454 36.2 36.4 36.1 35

Gross Pollutants 5,740 0 100 100 100 90

The concept stormwater management plan for the site, identifying the most appropriate options for various

areas, is shown in Figure 17-7. If a higher TN removal rate of 40% is targeted then the treatment area is

significantly increased. For example, the bio-retention garden area for Option 1 increases from 0.9% to 1.3%

of the contributing catchment areas. Larger bio-retention areas should be considered where possible on site.

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Figure 17-7. Conceptual Stormwater Treatment.

Potential End of Line Treatment Location

Stormwater Catchment Boundary


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17.6.3.1 Comparison to Existing Case

A comparison to the existing case stormwater pollutant loads and flows was conducted. The results are shown

in Table 17-8. As demonstrated by this table, due to the stormwater re-use, stormwater treatment and

proposed revegetation around the site the developed case pollutant loads are less than the existing case for

all pollutants despite likely increases in impermeable surfaces.

Table 17-8. MUSIC Results – Comparison to Existing Case Pollutant Loads.

Pollutant

Pollutant Load

(kg/year)

Existing Case Developed Case

IN OUT IN OUT

Flow (ML/year) 454 454 542 520

Total Suspended Solids 101,000 51,300 109,000 36,900

Total Phosphorus 134 91.5 171 85

Total Nitrogen 860 812 1,050 804

Gross Pollutants 3,310 633 5,740 0

17.6.3.2 Average Annual Flow Comparison

The MUSIC modelling predicted an increase in average annual flow of 88 ML/year due to the increased

impervious area. This reduced to 66 ML/year once rainwater tank demands were excluded. The average

annual results of GoldSim modelling for the existing and developed scenarios were added to the flow outputs.

The results are summarised in Table 17-9. Due to increased evaporation losses (due to diversion of additional

runoff into the dam), the increase in runoff is further reduced to 58 ML/year.

Table 17-9. Average Annual Flows.

Pollutant

Average Annual Flow (ML/year)

Dam Overflow

STP Overflow

Diversion Catchment

MUSIC Outflow

TOTAL

Existing Case 139.2 48.2 163.1 454 804.5

Developed Case No Dam Diversion

156.6 32.9 163.1 520 872.6

Developed Case With Diversion

(Diversion Threshold 6ML/day)

219.5 31.5 91.5 520 862.5

Developed Case With Diversion

(No Diversion Threshold) 309.5 31.5 0 520 861.0

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The same STP storages and irrigation rates were assumed for the existing and developed cases. The GoldSim

modelling had increased water demands, reduced irrigation demands and storage volumes than assumed in

the MEDLI modelling, which showed that no STP overflows would be likely. The following observations are

made in relation to Table 17-9:

Due to a reduction in water demand from the dam the average annual overflows are increased.

Due to reduced water demands and increased use of recycled water the volume of predicted overflow from the STP is significantly reduced. This will have significant impacts on the potential nutrient loads discharged downstream.

Diverting the additional catchment area to the dam reduces downstream flows by around 10 ML/year due to increased evaporation losses.

17.7 Stormwater Quantity Modelling - Preliminary Detention Basin Sizing

Preliminary detention basin sizing was conducted in accordance with the Queensland Urban Drainage Manual

(QUDM, 2008). The existing and developed case 63% and 1% AEP peak flows were calculated based on the

Rational Method to determine the volume of storage required for each catchment shown in Figure 17-1. To

simplify the analysis the dam diversion was not included. This will reduce the volume of detention storage

required for catchment E. The results are summarised in Table 17-10 and Table 17-11.

Table 17-10. Rational Method Calculations.

Catchment

Time of Con-

centration

(min)

Fraction Impervious 1% AEP Peak Flow

(m3/s) 63% AEP Peak Flow

(m3/s)

Existing Case

Developed Case

Existing Case

Developed Case

Existing Case

Developed Case

A 16.7 0.00 0.02 7.79 7.84 1.80 1.81

B 10.5 0.00 0.00 2.29 2.29 0.53 0.53

C 15.6 0.00 0.07 8.40 8.57 1.95 1.99

D 34.9 0.14 0.16 16.96 17.06 3.93 3.95

E 41.6 0.05 0.09 46.03 46.55 10.61 10.73

F 14.2 0.12 0.16 6.57 6.64 1.51 1.53

G 12.2 0.00 0.28 2.19 2.36 0.51 0.55

H 9.3 0.00 0.24 2.78 2.97 0.64 0.68

I 13.1 0.31 0.36 3.51 3.55 0.81 0.82

J 12.2 0.00 0.05 1.40 1.42 0.32 0.33

K 14.4 0.00 0.14 3.99 4.15 0.92 0.96

L 11.8 0.00 0.05 5.55 5.63 1.28 1.30

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Table 17-11. Preliminary Detention Basin Sizing.

Catchment

Detention Storage Required (m3)

Approximate Total

Rainwater Tank Storage

Likely Additional Stormwater Treatment

1% AEP 63% AEP (m3)

A 60 14 110 Buffer strips and some bio-retention gardens

B 0 0 0 n/a – camping sites

C 210 49 350 Buffer strips and some bio-retention gardens

D 260 60 180 Buffer strips and some bio-retention gardens

E 1726 398 700 Mix of bio-retention gardens, bio-retention

basins, grassed swales and wetland areas.

F 82 19 130 Mix of bio-retention gardens, bio-retention basins, grassed swales and wetland areas

G 170 39 260 Buffer strips and remaining roof and ground to

bio-retention gardens

H 141 32 180 Buffer strips and some bio-retention gardens

I 48 11 360 Mix of bio-retention gardens and wetland areas.

J 20 5 40 Buffer strips and some bio-retention gardens

K 184 42 310 Buffer strips and some bio-retention gardens

L 75 17 120 Buffer strips and some bio-retention gardens

The results from Table 17-11 show that the amount of rainwater tank storage being provided is significantly

greater than the 63% AEP detention storage required for all catchments. However, as the rainwater tanks

may be full prior to the storm event occurring, it is recommended that an additional 20 percent storage be

provided above the rainwater tank outlet, i.e. each 10kL tank for the villas should have a minimum size of 12kL,

with 2kL above the outlet, for catchments where bio-retention or wetland devices are not being provided.

Additional detention storage will also be provided by the bio-retention and wetland stormwater quality treatment

devices provided throughout the site. The greatest volume of detention storage is required for catchment E.

However, as 27 hectares from this catchment will be diverted towards the dam, the flows from this catchment

will be significantly reduced in the developed case.

17.8 Impacts associated with Climate Change

The potential impacts of climate change in the Mackay Whitsunday region are summarised in the 2014-2021

WQIP. The climate change trends for the Mackay Whitsunday region include:

Increased atmospheric CO2;

Increases in average air temperatures, more hot days and fewer cold days. On a national basis, Australia’s climate has warmed by 0.9ºC, with more extreme heat and fewer cool extremes (Bureau of Meteorology and CSIRO 2014). Projections for the Mackay Whitsunday region show that average maximum temperatures may increase by 1ºC by 2030 and 2ºC by 2070 (RPS 2014);

Annual rainfall is not expected to change, however the intensity of extreme events is expected to increase (Hilbert et al. 2014). Projections for the Mackay Whitsunday region indicate baseline (1995) 1 in 100 year rainfall events may occur every 70 years by 2030 and every 60 years by 2050 (RPS 2014);

The intensity (not frequency) of tropical cyclones is expected to increase (Hilbert et al. 2014);

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Evapotranspiration is expected to increase in all seasons (Hilbert et al. 2014);

Wind speeds are expected to increase across eastern Australia (Hilbert et al. 2014); and

Sea levels will continue to rise, and the frequency and height of storm surges are expected to increase (Hilbert et al. 2014).

Although the average annual rainfall is not expected to change, the increases in rainfall intensity during the

wet season, likely reductions in rainfall intensity in dry seasons and increases in evapotranspiration indicate

that an overall reduction in runoff is likely. The implications of climate change on the island’s water resources

are addressed in Chapter 18 – Water Resources.

17.9 Potential Impacts and Mitigation Measures

The following table provides an assessment of potential impacts and mitigation measures relating to water quality.

Table 17-12. Risk assessment matrix – water quality. Potential Impact

Significance of Impact:

Unmitigated

Mitigation Measure

Significance of Impact: Mitigated

Design Construction Operation

Acid Sulfate Soil

(ASS)

Disturbance

during

construction

activities

High (15) - ASS management

practices shall adhere to

the requirements of the

Queensland Acid Sulfate

Soil Technical Manual

Soil Management

Guidelines including

testing and monitoring

during construction

Implementation of a

Construction

Environmental

Management Plan

Excavation of areas

less than 5 metres

AHD is to be

undertaken in

accordance with the

Acid Sulfate Soils

Management Plan.

Low (5)

Increases in the

amount of

sediments that

may be exported

from the site.

High (15) - Prepare and comply with

an Erosion and Sediment

Control Program (ESCP).

Regular inspections

and maintenance will

be undertaken for

stormwater drainage

and treatment

systems.

Low (5)

Pollution arising

from site

activities.

High (15) - Install stormwater

treatment devices (e.g.

litter traps/vegetated

swales and buffers).

Monitoring of soil nutrient

levels to prevent leaching

of nitrogen and

phosphates at monitoring

points identified on Figure

17-3.

Regular inspections

and maintenance will

be undertaken for

stormwater drainage

and treatment

systems;

Use of pesticides,

herbicides is avoided

or limited to the dry

season.

Low (5)

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Potential Impact


Unmitigated

Mitigation Measure



Pollution arising

from the storage

or use of

hazardous

materials.

High (15) - All potentially hazardous

materials and waste (e.g.

waste oils, batteries, fuels

and chemical wastes etc.)

shall be stored in separate

containers located within a

bunded and roofed

hardstand area;

Any stormwater captured

within bunded areas used

for the storage, refuelling or

handling of fuels, waste or

other hazardous materials

shall be pumped out and

disposed of at an

appropriately licensed

facility;

Refuelling areas will be

bunded with a stormwater

containment system to

prevent discharge to soil or

waterways.

Establish a spill response

procedure.

All potentially

hazardous materials

and waste (e.g. waste

oils, batteries, fuels

and chemical wastes

etc.) shall be stored in

separate containers

located within a

bunded and roofed

hardstand area;

Any stormwater

captured within

bunded areas used

for the storage,

refuelling or handling

of fuels, waste or

other hazardous

materials shall be

pumped out and

disposed of at an


facility on the

mainland;

Refuelling areas will

be bunded with a

stormwater

containment system

to prevent discharge

to soil or waterways.

Establish a spill

response procedure.

Low (5)

Pollution from

liquid waste

(sewage) in the

event of

overloading,

electrical failure,

structural failure

or mechanical

failure

High (15) Waste water

treatment

infrastructure

shall be

located

outside of the

water supply

dam

catchment

Redundancy

in key aspects

of the

treatment

train e.g.

duty/standby

pumps

All critical infrastructure

shall be bunded

The wastewater

treatment plant will be

managed in

accordance with

conditions of an

environmental

authority for its

operation.

Temporary bunding

and wet weather

storage requirements

shall be utilised to

mitigate the risk of

overflow with any

water collected to be

pumped out and

disposed of at an


facility on the

mainland.

Back-up generators

shall be provided for

use during power

failures

Low (5)

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Potential Impact


Unmitigated

Mitigation Measure



Recycled water

discharged to

surface water

Medium (9) - 12 ML wet weather storage

to be constructed to contain

flows during occasions

when irrigation is

unavailable due to wet

weather

All wastewater will be

treated through an

appropriately sized

plant with effluent

quality suitable for

public irrigation (Class

A+) with nutrient

removal

Where discharge of

recycled water is

required, monitoring

of quality of all

discharges shall be

conducted

Low (2)

Mismanagement

of irrigation

activities

Medium (9) Areas for

irrigation are

to be located

outside of the

Dam

catchment

area

- Recycled water shall

be treated through an

appropriately sized

plant with effluent

quality suitable for

public irrigation (Class

A+) with nutrient

removal

Irrigation activities

shall be conducted in

accordance with an

Irrigation

Management Plan

Low (2)

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DRAFT

17.10 Summary

Water quality is naturally variable, and is dependent on numerous factors such as land use, catchment

management practices, antecedent conditions, soil types, climatic and seasonal factors and in-stream

processes. The water quality objectives for the assessment were sourced from the Environmental Protection

(Water) Policy 2009 - Proserpine River, Whitsunday Island and O'Connell River Basins Environmental Values

and Water Quality Objectives, and associated plans. The Water Quality Guidelines for the Great Barrier Reef

Marine Park 2010 were also referenced. The majority of Lindeman Island is classified as Whitsunday Island

freshwater with High Ecological Value (HEV) for Aquatic Ecosystems, however the existing and proposed

developed area of Lindeman Island (with the exception of glamping area on the western coast) is not included

in this area and is therefore classified as Moderately Disturbed Freshwater.


monitoring, however despite this two rounds of event based water quality testing were able to be conducted

at the site within the waterways. The water quality testing identified that that current water quality meets the

specified objectives. In June, at site LIND06 there was an elevated level of TSS. Further additional water

quality testing is proposed prior to construction, with the inclusion of an additional monitoring point LIND07

near the proposed glamping facilities. The proponent has also made a commitment to completing a baseline

marine water quality sampling program. The objective of the program would be to identify the environmental

values of receiving waters and set objectives and indicators relevant to the protection of those values.

MUSIC modelling undertaken as part of the EIS has identified that despite marginal increases in impermeable

surfaces, stormwater quality across all measures (Total Suspended Solids, Phosphorus, Nitrogen and Gross

Pollutants) is predicted to improve as a consequence of proposed stormwater treatment devices and

measures. These measures include rainwater tanks, vegetated buffer strips, bio-retention gardens, bio-

retention basins, constructed wetlands, Gross Pollutant Traps and revegetation of cleared areas. Further the

proposed golf course will be managed in accordance with the Golf Course Management Plan and Irrigation

Plan to ensure any nutrients will be taken up by the existing vegetation.

The stormwater and water management strategy for the Lindeman Great Barrier Reef Resort aims to reduce

the pollutant load being discharged to streams that drain to the Great Barrier Reef Marine Park. Specifically,

stormwater and water management strategies will be adopted that:

Re-uses rainwater, reducing potable water demand and stormwater pollutant loads;

Treats and re-uses wastewater for non-potable uses on site;

Minimises the potential sources of stormwater pollutants;

Treats stormwater runoff to remove sediment and nutrient load;

Replicates existing flow patterns;

Reduces potential for scour and erosion; and

Integrates open space with stormwater drainage corridors and treatment areas to maximise public access and recreation and preserve waterway habitats and wildlife corridors.

Accordingly, no long term irreversible water quality impacts, both terrestrial or marine, are likely to arise from

the development.

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